Organic light-emitting diode (OLED) display, which is also referred to as organic electroluminescence display (OELD), is a most promising display technology due to its advantages such as good color contrast, active light-emitting, wide viewing angle, thinness, fast response speed and low power consumption. However, in an OLED device, it is possible for an organic light-emitting layer and an electrode to fail if they encounter with water or oxygen. Accordingly, thereby service life of the OLED device is affected greatly. Thus the OLED device generally needs to be well sealed. In an early packaging method, since it has been impossible to ensure a good sealing, typically a desiccant or drier sheet has been provided inside the OLED device. However, it has been unnecessary to use the desiccant or drier sheet inside the OLED device since frit sealing has been used as a packaging adhesive, as the frit is heated and melted by using a moving laser beam and can form a seal structure with good air-tightness.
However, there is a new problem for the OLED package structure using a frit as the packaging adhesive.
As shown in FIG. 1, an OLED package structure 100 using the frit as the packaging adhesive includes a substrate 110, a cover plate 120 and a frit packaging adhesive 130. An organic light-emitting element 111 is formed on the substrate 110. Typically, there is a spacer 112 inside the package structure for keeping a uniform distance between the substrate 110 and the cover plate 120 of the OLED.
Generally, the spacer should not be too thick. This is because, as shown in FIG. 2, evaporation is needed during the manufacture of the OLED. During the evaporation, a mask 240 is typically used for protection, and an organic film layer 213 (and an inorganic film layer) is formed on the substrate through an opening of the mask 240 by the evaporation. During the evaporation process, the mask 240 contacts the spacer 212. Thus, if the spacer 212 is too thick, unwanted evaporation material develops on the left side and the right side of the organic film layer 213. The unwanted evaporation material may cause poor display quality, such as poor color mixture of the display device.
Therefore, it is typically required to manufacture a thinner spacer. Moreover, the frit used as the packaging adhesive is also required to be thinner. This is because, as shown in FIG. 3, if the thickness of the frit 330 is not reduced, the frit 330 on the left side and the right side of the OLED package structure 300 is thicker and the spacers 312 in the middle are thinner, the cover plate 320 may be warped. In this case, a Newton ring effect which affects image quality of the finally formed display device may be generated between the cover plate 320 and the substrate 310. However, the frit 330 has to be sufficiently thick to ensure packaging requirements.